Physical methods of cryptography: security beyond mathematical limits

Background: 

Advancing digitalisation brings new security risks that can soon only be inadequately controlled with the encryption methods currently in use. They will reach their limits at the latest with the advent of quantum computers. However, key transmissions based on physical principles offer a future-proof alternative. A lot of research funding is currently being channelled into the development of such methods and there is great euphoria about their performance. However, due to the different approach and the physical knowledge required, misunderstandings arise. In our project, we want to dispel such ambiguities and present various physical encryption methods. We highlight their strengths and weaknesses and show which scenarios they are suitable for. 

A comparison of four physical methods: 
 
•       QKD with entangled photons: Quantum entanglement makes eavesdropping attempts immediately recognisable. 

•       QKD with BB84 protocol, where the transmitter side determines the randomness and thus the polarisation of the photons. 

•       Secure hardware (e.g. SSD with AES-256): Simple, hardware-based key transmission. 

•       Radio channel properties: Key generation through the reciprocity of radio signals. 

We answer the following questions for each method:

•       How secure is it, how well does it work in defence against attacks? 

•       Is it functional and practical? 

•       Is it economically viable, how easy is it to implement? 

•       What is the range and can data be transmitted efficiently? 

•       How suitable is it for everyday use? Does it deliver stable results under different conditions and is it flexible and widely applicable? 

 
Conclusion: Under the direction of FH-Prof. Univ.-Doz. Dipl.-Ing. Dr Ernst Piller, UAS lecturer at the St. Pölten UAS, the strengths and weaknesses of physical methods of cryptography are being investigated.